Development of materials for handling hot glass

Abstract

For glass bottles to compete with plastic ones they need to be very much lighter. As their present weight is often constrained by their current strength, the glass they are made from needs to be very much stronger. In its virgin state glass is very strong, but handling bottles during manufacture introduces minute flaws, lowering their strength considerably. The aim of this work has been to gain a greater understanding of the meclianisms of thermal and mechanical damage and so to improve existing, and develop new hot glass handling materials which will reduce the amount of damage to the glass during hot-end handling To help gain an understanding of the interaction between thermal and mechanical damage mathematical modelling using finite difference techniques was utilised. Experimental investigations of how controlled contact, including thermal shock, weakened high strength glass were also undertaken. It was concluded from these investigations that the nearest to the ideal a real hot glass handling material could approach would be a material which produces mechanical damage which is limited to such a size that the thermal stresses produced by that material do not exacerbate the damage. A dimensionlessg roup was identified which helped to assessif a material had a selection of material properties which render it a likely hot glass handling material. Zirconium and Titanium were identified as possible hot glass handling materials. Carbon based materials proved to be the best handling materials but they have a limited life as they suffer oxidation in use. The oxidation resistance of various Carbon based materials was investigated with thermal gravimetric analysis and a test was designed to assess the strength retention of laminated Carbon-Carbon composites. Various coatings were developed to increase the life of existing hot glass handling materials. A Tit anium /graphite composite was developed in which the Titanium acted as an oxidation resistant skeleton and the graphite provided optimum glass handling ability.